The present invention relates to circuitry formed on substrates. More specifically, the present invention relates to gate lines that control conductivity in semiconductor lines.
Lewis, A., and Wu, I-W., "Polysilicon TFTs for Active Matrix Liquid Crystal Displays," IEICE TRANSACTIONS, Vol. J76-C-II, No. 5, May 1993, pp. 211-226, describe fabrication of polysilicon (poly-Si) thin film transistors (TFTs) and poly-Si active matrix liquid crystal display (AMLCD) pixel designs. Section 2.3 describes process flow and device architectures in relation to FIG. 2, which shows TFT device cross-sections. FIG. 10 shows a typical AMLCD pixel, and section 4 discusses poly-Si TFT AMLCD pixel design issues. Of techniques to reduce leakage, the use of multiple gates in a TFT is the simplest; FIG. 11 illustrates the transfer characteristics of TFTs with 1, 2, 4, and 8 gates, all with the same total gate length.
Wu, I-W., "High-definition displays and technology trends in TFT-LCDs," Journal of the SID, Vol. 2, No. 1, 1994, pp. 1-14, describes various liquid crystal displays (LCDs), focusing on AMLCDs with TFTs. FIGS. 2-5 show general features of conventional TFT-AMLCDs. As described in relation to FIG. 3, TFTs act as switches controlled by gate electrodes, connecting data lines to pixel electrodes. FIG. 11 shows a schematic cross section of a poly-Si TFT AMLCD, described in section 7. FIG. 12 shows a double-gate poly-Si TFT to reduce leakage current.